DNP was banned in 1938 by the US Food and Drug Administration (FDA) as being a danger to human health.

DNP is an industrial chemical which has legitimate uses in pesticides and munitions but it is not a licensed medicine “in the world and certainly not in the UK” and its use has been likened to playing Russian roulette, according to consultant physician Professor Simon Thomas.

He told the jury: “I think this refers to the fact that there is uncertainty around what particular dose will give the desired effect or produce severe or life threatening toxic effects.

“It is about what the dose will do to any individual taking a substance.”

He added: “They could not predict in the 1930s and I do not think now what a safe dose could be for an individual - the lower the better - but what would be safe enough is uncertain.”

Despite the risks some bodybuilders have used DNP because having lower body fat helps show off their muscle definition, the court heard.